A conventionally well-known transparent conductive film is what is called a conductive glass, which includes a glass substrate and an ITO coating (indium-tin complex oxide coating) formed thereon. When an ITO coating is formed on a glass substrate, the coating can be deposited while the glass substrate is heated at 200° C. or higher, generally, 300° C. or higher. In this case, therefore, an ITO coating with a thickness of 130 nm and a low surface resistance of 10 Ω/square or less (a specific resistance of 1.3×10−4 Ω·cm) can be easily obtained.
However, the glass substrate, which has low flexibility and workability, cannot be used in some cases. In recent years, therefore, transparent conductive films having an ITO coating formed on various organic polymer film substrates such as polyethylene terephthalate films are used because of their advantages such as a high level of flexibility, workability, and impact resistance, and light weight.
The preferred level of specific resistance and surface resistance, required of the ITO coating-bearing transparent conductive film, varies with the use of the transparent conductive film. However, the ITO coating formed on the organic polymer film substrate has become required to have the same level of specific resistance and surface resistance as that of the ITO coating formed on the glass substrate. For example, film displays have been studied recently. For such display applications, the ITO coating formed on the organic polymer film substrate has been required to have a low resistance of 10 Ω/square or less per 130 nm thickness, which is the same level as that of the ITO coating formed on the glass substrate. Transparent electrode applications for introduction of light into solar cells, particularly, transparent electrode applications for thin film solar cells require a resistance of 10 Ω/square or less, a high transmittance in the near-infrared region, and high reliability under a high-temperature, high-humidity atmosphere.
A variety of processes are proposed for the ITO coating-bearing transparent conductive film (Patent Documents 1 to 5).